Conventionally, a fish is filleted into three pieces of two fillets and a backbone part by a fish processing device called a filleting machine. The two fillets of quality meat are served as food while the backbone part is used in a form of fish meal or as a material for minced fish meat after collecting the meat, since the backbone part, as it is, is difficult to be served as food even though the quality meat is attached to it.
For example, according to the Patent Document 1, the fish is filleted into three pieces by the filleting machine to obtain two fillets and a backbone part. The backbone part is crushed and is minced together with the fillets to be used as a calcium-fortified ground fish-meat product or a calcium-fortified hamburger steak by which calcium contained in the bone can be consumed. Similarly, according to the Patent Document 2, the backbone part is crushed into a paste-like material and the fish bone paste is added to the fillets to obtain the minced fish-meat product to prepare the calcium-fortified ground fish-meat product as the ground fish meat prepared by using only fillets contains little calcium.
According to the Patent Document 3, the backbone part of the fish, which is filleted into three pieces, has a considerable amount of meat attached to it, and the attached meat is collected by a fish meat collecting machine to use the fish meat as an ingredient for ham and sausages. Further, the backbone after collecting the meat is crushed into a paste-like material, and the fish bone powder in the state of the paste-like material is used for the ground fish-meat product.
Further, the Patent Document 4 discloses a method and a device for separating the quality meat, which is attached to the backbone of the fish when filleted into three pieces, from the backbone part. To be specific, the backbone part is placed on a guide means arranged parallel on right and left sides at an interval in the state that a tail side of the fish is oriented in a conveying direction, and the backbone part is fed to a pair of upper and lower circular cutters arranged at a vertical interval having the same height as the diameter of a vertebral column of the backbone part so that the upper and lower circular cutters may separate back extensions and belly extensions having quality meat, from the vertebral column.